Air nozzle and porting for combustion chamber liners



June 6, 1950 D. MGMAHAN 2,510,645

AIR NOZZLE AND PORTING FOR COMBUSTION CHAQIBER mums Filed Oct. 26, 1946g 'G C) Irwventor: Ken ton D. Mc M ah an,

His Attorrwey.

Patented June 6, 1950 AIR NOZZLE AND PORTING FOR COMBUSTION CHAMBERLINERS Kenton D. McMahan, Scotia, N. Y., assignor to General ElectricCompany, a corporation of New York Application October 26, 1946, SerialNo. 705,866

8 Claims.

This invention relates to ombustion chambers or combustors forgenerating hot gases under pressure, as for use in thermal powerplantssuch as gas turbines. More specifically, the invention relates to animprovement in the Nerad type combustor, described generally in patentapplication Serial No. 501,106, filed September 3, 1943, in the name ofAnthony J. Nerad, now abandoned, also a continuation-in-part Serial No.750,- 015, filed May 23, 1947.

The Nerad combustor is so designed that high velocity jets of combustionsupporting fluid are directed in an exactly radial direction into thecombustion space from inlet ports in a substantially cylindrical liner,which defines the combustion space. By proper location and dimensioningof the ports, a characteristic flow path 'is obtained which includes atore or smoke ring vortex at the closed end of the liner, theestablishment and maintenance of which is essential to eflicientoperation of the combustor. A most important factor affecting the toreis the uniformity with which air is supplied to the ports in the liner.The afore-mentioned Nerad application describes various ways to securethe required uniformity of air supply. This problem is aggravated to ahigh degree when the air supply approaches the closed or dome end of theliner in an unsymmetrical manner, perhaps the worst condition being thatin which the approach velocity is at right angles to the axis of theliner. In building a gas turbine powerplant with the components soarranged that this approach angle could not be avoided, it was foundimpossible to make a Nerad type combustor operate properly because ofthe extreme non-uniformity of air flow around the liner.

Accordingly, an object of the invention is to provide an improvedpressurized combustor of the Nerad type which is substantiallyinsensitive to variations in the direction from which the combustion airapproaches the air inlet ports, and which gives more stable combustioncharacteristics with uniform temperature distribution and a lowerover-all pressure drop through the combustor.

Another object is to provide means for insuring a satisfactory flow ofair to the inlet openings in the end dome and the liner of thecombustor.

A further object is to provide an improved liner for a Nerad combustorwhich will operate .efficiently regardless of variations in the angle atwhich the combustion air approaches the inlet ports of the liner.

A still further object is to provide an improved I Referring now to Fig.1, my combustor assembly comprises a thin-walled cylindrical member Iopen at either end. At one end the cylinder l is provided with a flangesecured by suitable threaded fastenings 2 to a corresponding flange ofan inlet elbow or air adapter 3. While the inlet elbow 3 may be formedas a casting, it is shown in Fig. 1 as fabricated from thin sheet metalprovided with a boss 4 defining a threaded opening coaxial with thecylindrical casing l. The elbow 3 constitutes an inlet conduit throughwhich air under pressure enters from a suitable source, such as acompressor (not shown), as indicated by the arrow 5.

For introducing fluid fuel into the combustion space a spray nozzle isprovided, as indicated at 6. This nozzle may be of any suitable type.Where the fuel used is a liquid such as kerosene or gasoline, theso-called duplex nozzle may be used, as described in patent applicationSerial No. 622,604, filed October 16, 1945, in the names of Charles D.Fulton and David C. Ipsen. Such nozzles require two supply conduits Iand 8. It should be understood that many other types of nozzle may alsobe used; and the specific details of the spray nozzle are not materialto an understanding of the present invention. Asshown in Fig. 1, thenozzle tip 9 projects into the inlet elbow 3 coaxial with the casing I,and has a portion threadedly engaging the central. opening in boss 4.The nozzle 6 discharges the fluid fuel in the form of a hollow cone,indicated diagrammatically at 30 in Fig. 1.

Supported coaxially in the cylindrical outer casing I is an inner linerindicated generally at Hi. This comprises a generally cylindrical butpreferably somewhat tapered casing having its smaller end adjacent theinlet elbow 3. The construction of the inner liner may be seen byreferring to Fig. 2 in conjunction with Fig. 1. It is formed by punchinga plurality of longitudinal rows of combustion air inlet ports ll, theprecise proportions and arrangement of which is specifled moreparticularly in the above-mentioned Nerad application. Between adjacentrows of combustion air ports II are longitudinal rows of nozzles l2,formed by striking the metal of the liner outwardly as shown in Fig. 1so as to define cooling air inlet nozzles arranged to admit air in themanner indicated by the arrows l3 in Fig. 1. This cooling air l3 forms athin continuous film of pure comparatively cool air flowing over theinner surface of the liner it so as to keep hot products of combustionand incompletely burned fuel particles from contact with the relativelycool metal of the liner. This arrangement prevents deposition of carbonparticles as described in the above-mentioned Nerad application. At thedischarge end of the liner, there is provided a row of spaced struck-outportions or "dimples" ll which serve a purpose noted hereinafter.Parallel to the discharge edge of the liner and spaced intermediate thedimples I4 and the last circumferential row of combustion air inlets IIis a row of plain circular ports IS, the purpose of which will also benoted hereinafter.

The liner, formed as shown in Fig. 2, is rolled upto definea somewhattapering cylinder as in Fig. 1, the side edges It being secured togetherby suitable means, as for instance seam-welding.

In accordance with my invention, each of the combustion air inlet portsii is provided with a short nozzle ll projecting radially outward fromthe liner. The arrangement of these nozzles is indicated in Fig. 1. anda single nozzle is shown to an enlarged scale in Fig. 3. The nozzles mayadvantageously be secured to the liner by welding to a struck-out flange22 provided around the edge of each port ll.

Research studies made to improve the basic form of the Nerad combustor,and to adapt it to many different gas turbine powerplants of varyingconfiguration and characteristics, have shown that the Nerad combustionchamber, in its very simplest form, is somewhat sensitive to changes inthe direction from which the air supply approaches the inner liner. Formost efiieient and successful'operation of this type of combusto it isessential that the combustion air entering the combustion space definedwithin the liner l through the ports ll shall form discrete jets withtheir axes approaching very closely to the radial direction. In otherwords, it is desired that the air inlet ports I I produce jets havingtheir axes substantially in a plane normal to the longitudinal axis ofthe liner ll, the axes of the jets from any given circumferential row ofports I i meeting at the axis of the liner.

When the configuration of the powerplant permits the air discharged fromthe compressor to be conducted to the combustion chamber so as toapproach the inner liner in a substantially axial direction, then theproblem of supplying combustion air uniformly to allthe ports H iscomparatively simple. 0n the other hand, when the arrangement of thepowerplant requires that the combustion air approach the combustor at a90 degree angle to the axis of the combustor, as represented in Fig. 1,or in some other non-symmetrical manner, then special measures must betaken to insure that proper distribution of the air is obtained. If thesupply of combustion air to the ports H is not uniform, then thecombustion fllciency decreases, the temperature distribution of the hotgases becomes non-uniform, resulting in hot spots which greatly shortenthe length of life of the liner and other parts, and other undesirablecharacteristics appear.

Accordingly, an important object of the invention is to provide meansfor stabilizing the direction of the combustion air jets entering thecombustion space within the liner Ill through the ports H. I have foundthat this may be achieved by providing, the nozzles ll extending astraight cylindrical discharge portion and a well-rounded entranceportion. It is desirable that the discharge edge is of the nozzle lie ina plane exactly normal to the axis I! of the nozzle. Likewise, the axisiii of the nozzle must be normal to the axis of the liner, as indicatedin Fig. 1. The radius of curvature of the nozzle inlet mayadvantageously be of the order of one quarter the inside diameter d ofthe nozzle. It will be apparent that this nozzle has a contracting inletportion, and a non-expanding discharge portion. This is important, sinceit is desired to produce a high velocity jet of good penetrating power.

A considerable amount of research has been done to determine the effectof changing the proportions of the nozzle. This work has shown that thelength of the nozzle It must be of the order 01' of the inside diameterd. While increasing the length of the nozzle beyond this value does noharm from an aerodynami standpoint, neither does it make any appreciableimprovement; and it has the serious disadvantage of increasing therequired diameter of the combustor as well as the weight. I have foundthat with nozzles proportioned as described, the angle at which thefluid approaches the nozzle may vary from zero degrees to 90 degreeswithout causing the discharge angle to deviate more than perhaps twodegrees. In Fig. 3 the "approach angle is identified as the acute anglea which the approach velocity vector 20 forms with the axis IQ of thenozzle. The discharge angle is defined as the acute angle b which theleaving velocity vector 2| forms with the axis l9.

As described in the above-mentioned Nerad application, it isparticularly important that the first circumferential row of ports I ladjacent the fuel nomle end of the combustor produce stable discretecombustion air jets meeting exactly at the center of the liner, in orderthat the primary portion of v the air will flow axially back towards thenozzle tip 9 in the manner indicated by the arrows 23 in Fig. 1. Forthis reason, it is essential that the first circumferential row ofnozzles ll be very carefully proportioned as described above.

For succeeding circumferential rows of nozzles, the characteristics ofthe jets produced become less and less Therefore, it is possible tosomewhat shorten the axial length of the nozzles below the minimumlength specified above. Accordingly, in Fig. 1 the axial length of theair nozzles II decreases progressively from the closed or fuel nozzleend of the liner to the open discharge end. This arrangement isparaciaeec ticularly advantageous when the liner is ,some-' what taperedand is contained within a straight cylindrical outer housing, as inFig. 1. It will be apparent that the tapered inner liner ill forms anannular air supply space with the cylindrical outer housing I whichdecreases progressively in' cross-sectional area along the length of theliner. This is desirable since the air entering the inlet ports causesthe quantity flowing in the supply space 24 to progressively decreasealong the length of the liner. By properly correlating the taper of theinner liner with the shape of the outer housing I, it is possible tokeep the axial velocities of the air flow in the chamber 24substantially uniform, thus further helping to insurev a uniform supplyof air to the nozzles I'l by making the velocity of approach to eachnozzle substantially uniform. Such uniformity is also desirable withrespect to the cooling air l3 which enters the liner through thestruck-out nozzle portions |2.

From the above, it will be apparent that the nozzles ll may all be ofthe same axial length, if desired, and if the increase in size andweight is not objectionable.

The inlet or fuel nozzle end of the liner I is closed by a hemisphericalend dome 25. This may advantageously be arranged in accordance withapplication Serial 644,888, filed February 1, 1946 in the name of WalterL. Blatz. This dome structure has a central opening surrounded by anaxially extending flange 26 adapted to slide snugly over the cylindricalnozzle tip 9. The dome is provided with one or more circumferential rowsof nozzles formed by struck-out tongue portions 21. The function ofthese nozzles is to form a thin film of cooling and insulating airflowing over the inner surface of the dome 25 so as to prevent carbondeposition thereon. In other words, the nozzles 21 perform a somewhatsimilar function for the end dome 25 as is performed for the liner l0 bythe cooling air nozzles l2. As described more fully in theabove-mentioned Blatz application, the cooling and insulating air fromthe nozzles 21 flows radially inward in the manner of the arrows 28,across the exposed end surfaces of the nozzle tip 9, after which itreverses its direction and flows radially outward, as indicated by thearrow 29.

While the member 25 is referred to herein as a dome, I intend this termto include generally closures for the fuel nozzle end of the liner ofshapes other than the hemispheral configuration shown in Fig. 1, forinstance substantially flat disc members, as disclosed in theabove-mentioned Nerad application.

Since the performance of the combustor is also materially affected bythe uniformityof air flow into the primary combustion zone definedwithin the dome 25, it is important to insure a uniform supply of air tothe end dome air inlet nozzles 21. To this end, I provide a suitablydesigned shroud member 3| which completely surrounds the end dome 25 andmay be secured to the liner by a weld at 32. Of course with thisarrangement, suitable U-shaped cutouts are required in the edge of theshroud so that it can be slipped over the small end of liner H) in themanner shown in Fig. 1, with the first circumferential rows of nozzles|'l fitting into the respective cutouts.

The shroud 3| is provided with a number of spaced air inlet ports 33.These are of such a size, location, and number that the air suppliedthrough the inlet elbow or air adapter 3 will flow uniformly into thespace or plenum chamber 33 defined between the end dome 25 and theshroud 38, with substantially no difference in pressure between the airin the elbow 3 and that in the plenum chamber 3i. Thus withsubstantially no pressure drop across the air inlet openings 33 in theshroud 3|, the velocities through these ports will be low and the airwill have a chance to diffuse uniformly throughout the chamber 34.

In order to secure uniform distribution from the inlet elbow 3 to theannular plenum chamber 24 which supplies air to the combustion airnozzles l1 and the cooling air nozzles l2, it is also important that theouter configuration of the shroud 3| be matched to the configuration ofthe elbow 3 so that air entering in the direction of the arrow 5 willflow around the shroud 3| and enter the plenum chamber 2d uniformlyaround the circumference thereof. Because of the many variablesinvolved, it is not possible to state specifically the precisedimensions and configuration required for the end dome shroud 3| and theinlet elbow 3. Analysis of the specific powerplant arrangement withwhich the combustor is to be used, supported by actual testing,

of models, is ordinarily required to ascertain the precise relativeshapes required for the shroud and elbow, as well as the number, sizeand location of the shroud air inlet ports 33. I have however found thatgood results may be obtained with an arrangement substantially as shownin Fig. 1.

Aswill also be seen in Fig. l, th shroud 3| is provided with a centralopening having a plurality of circumferentially spaced bosses 35 weldedaround the outside thereof. These bosses are adapted to be secured. bysuitable threaded fastenings 36 to the ring 4 provided on the outer wallof elbow 3. It will be seen that the shroud 3| thus serves to supportthe inlet end of the liner Ill.

The plain circular ports l5 at the discharge end of liner III aretrimmer holes, provided for the purpose of facilitating final balancing"of the combustioncharacteristics of the apparatus. It will be observedthat the combustion inlet nozzles I1 and the cooling air nozzles l2 arearranged in an entirely uniform symmetrical manner. It may sometimes befound, when the combustor is built and tested, that the temperaturedistribution in the hot gases discharged from the liner is not exactlyuniform. This may be corrected by suitable selection of the size.number, and location of the trimmer holes. since these holes have noassociated nozzles corresponding to the nozzles ll, they may be readilypunched in any size and arrangement found necessary to achievecompletely uniform temperature distribution. The precise arrangementrequired can be determined only by analysis and testing of a model. 4

The discharge end of liner I0 is supported in the following manner. Thedownstream end of the outer casing l is provided with a flange adaptedto be secured by suitable threaded fastenings 31 to a cooperating flangeat the upstream end of a discharge elbow indicated generally at 38.Between the coupling flanges is arranged an annular member having anouter circumferential portion 39 disposed between the cooperatingflanges. The inner circumferential portion of this annular member isspun or otherwise shaped to form an annular convolution 40 and acylindrical portion 4| coaxial with the downstream end of the casing Iand the discharge end of the liner ill. The dimples l4 formed in thedischarge edge of liner H] are of such a radial height that the outsidediameter of the discharge edge, measured over the dimples, issubstantially the same or very slightly less than the inner diameter ofthe cylinder 4|. As will be obvious from a consideration of Fig. 1, thedischarge end of liner I is thus supported in a longitudinally slidablemanner within the ring 4i. Since the nozzle end of the liner is heldrigidly by the threaded fastenings 36, the discharge edge of the linerin slides axially to a limited extent within the supporting ring 4!, asthe length ,of the liner-changes as a result of differential thermalexpansion between the hot liner and the comparatively cool outer casingI. The annular convolution provided in the support member permitsdifferential thermal expansion between the inner cylindrical portion 4|and the cooler circumferential outer portion 39.

The cylinder 4| also serves to support the inner liner 42 of thedischarge elbow assembly 38, in a manner which will be obvious from aconsideration of Fig. 1. The outer casing 43 of the elbow assembly maybe provided with a flange at the downstream end secured by threadedfastenings 44 or other suitable means to a cooperating flange of aconduit 45, which may for instance be the inlet to a gas turbine. Thedownstream end of the inner liner 42 is provided with a circumferentialrow of dimples 46 which may be similar in structure and are identical infunction to the struck-out portions l4 provided in the discharge edge ofthe liner l0. A supporting ring 39, 40, 4| supports the downstream endof the inner liner 42 and the upstream end of the liner a in the mannerdescribed above in connection with the discharge end of the liner l0 andthe upstream end of liner 42.

The. supporting ring members for the respective inner liners areprovided with a circumferential row of openings 41 through which coolingair flows from the plenum chamber 24. This coolant flowing through theannular space defined between the respective members 42, 43 and 45, 45aserves effectively to cool the inner liners and to reduce thetransmission of heat from the inner liners to the outer casings. It willbe obvious that the combustion and cooling air flowing through theplenum chamber 24 likewise reduces the transmission of heat to the outercombustor housing I. It should also be noted that the dimples l4cooperate with the supporting ring 4| to form a circumferential row ofopenings through which cooling air flows from plenum chamber 24 in themanner of the arrows 48 so as to form a cooling and insulating film overthe inner surface of elbow liner 42. Similarly, some of the cooling airindicated by the arrows 49 flows through the spaces defined between thedimples 46 in the manner of the arrows 50 to form a cooling andinsulating film on the inner surface of liner 45a.

The air inlet elbow 3 may be fabricated from sheet metal or cast ofaluminum, magnesium, or other suitable metal. Ordinarily it is necessarythat the inner combustor liner Ill and the end dome 25 as well as theconduit liners 42 and 45a be made of expensive temperature-resistlngalloys such as various stainless steels. I have found however that themarked improvement in uniformity of temperature and stability of gasflow achieved with my invention makes it possible to fabricate the linerIII of low temperature metals, such as ordinary mild steel. The outerhousings I, 43 and 45 may be made of ordinary inexpensive sheet metalstock.

While the invention has been described as used for burning a liquid fuelin air, it will be obvious that it may also be used for effectingsimilar heat-releasing reactions between other types of fluid reactantsand other reaction supporting gases besides air. Therefore it isintended that the term fluid fuel" in the appended claims be interpretedto include all fluid reactants capable of being used in my combustor,and that the term air" be considered to include otherreaction-supporting gases as well.

Experience with combustors embodying my invention, both in laboratorytests and in actual operation in a gas turbine powerplant, shows that itprovides simple, comparatively light, yet very effective means forstabilizing the operation of a Nerad type combustor, producing uniformlyefllcient combustion and temperature distribution over a wide range ofoperating conditions and having very little or no sensitivity to changesin the direction from which the air supply approaches the combustor. Atthe same time, my improved construction remains easy and comparativelycheap to manufacture. The arrangement of the combustor facilitatesdisassembly for easy inspection and servicing of the inner liners, whichin a' gas turbine powerplant are usually the parts most subject todeterioration. My invention also provides a simple and effective methodfor supporting the various high temperature inner liners from the coolerouter housing members.

While the present invention has been described as an improvement in thecombustor invented by Mr. A. J. Nerad, it will be obvious to thoseskilled in the art that it may also find application in other combustiondevices operating at high pressures and with substantial pressuredifferentials across the liner defining the combustion space, thecombustion supporting fluid being admitted with high spouting velocitythrough ports or nozzles the size and location of which needs be verycarefully chosen in order to obtain a desired flow path within thereaction space. In any such combustor, the invention makes possible theaccurate establishment of a jet having a precisely determined direction,and being insensitive to irregularities or unsyinmetricity of the flowof fluid approaching the liner.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. In a fluid fuel combustor of the type having an elongated liner ofcircular cross-section tapering from a minor diameter at one end to amajor diameter at the other end and defining a combustion space withinand having a plurality of circumferentially spaced longitudinal rows ofports for admitting combustion air in discrete jets, a cylindrical outerhousing enclosing the liner and spaced therefrom to define an air supplychamber decreasing progressively in crosssectional area from the smallerend of the liner towards the larger end, an end dome member closing thesmaller end of the liner and having ports for admitting cooling air tothe combustion space adjacent the closed end thereof, and means foradmitting fluid fuel to the combustion space, the combination ofnon-expanding nozzle means associated with each of the combustion airinlet ports for stabilizing the direction of jet discharge into theliner, each of said nozzles having its axis normal to the axis of theliner and projecting from the inner surface of the liner radiallyoutward into the air supply chamber, each of the nozzles in thecircumferential row next adjacent the closed end of the liner having arounded contracting inlet portion and an axial length of the order offive eighths the inner diameter of the nozzle, the axial length of thenozzles in succeeding circumferential rows decreasing progressivelytowards the discharge end of the liner whereby the spacing of the inletends of the nozzles from the outer housing provides unimpeded access ofthe air to the inlets, conduit means for supplying air to the supplychamber in an unsymmetrical, manner, and shroud means within saidconduit and spaced therefrom and enclosing the end dome, said shroudbeing shaped to cooperate with said conduit to define a passage fordirecting air uniformly into the supply chamber and said shroud havingports foradmitting air uniformly to the cooling air ports of the enddome.

2. In a fluid fuel combustor of the type having an elongated liner ofcircular cross-section defining a combustion space Within and having aplurality of circumferentially spaced longitudinal rows of ports foradmitting combustion air in discrete jets, an outer housing enclosingthe liner and spaced therefrom to define an air supply chamber, an enddome member closing the inlet end of the liner and having ports foradmitting cooling air to the combustion space, and means for supplyingfuel to the combustion space adjacent the closed end thereof, thecombination of nozzle means associated with each of the combustion airinlet ports adjacent the closed end of the liner for stabilizing thedirection of jet discharge, each of said nozzles having its axis normalto the axis of the liner and projecting from the inner surface of theliner radially outward into the air supply chamber and beingof a lengthsuch that the air jet therefrom is discharged in a substantially radialdirection into the combustion space regardless of the direction of fluidapproach to the nozzle, conduit means for supplying air to the supplychamber, and shroud means within said conduit enclosing the end dome andspaced from the conduit and from the end dome, said shroud being shapedto cooperate with said conduit to define a passage for directing airuniformly into the supply chamher and said shroud having ports foradmitting air uniformly to the cooling air ports of the end dome.

3. In a fluid fuel combustor of the type having a cylindrical outerhousing spaced radially from an inner elongated liner of circularcrosssection tapering from a minor diameter at one end to a majordiameter at the other end and defining a combustion space within, saidliner having a plurality of circ-umferentially spaced longitudinal rowsof ports adapted to admit combustion air in discrete radial jets, and anend dome member closing the small end of the liner, the larger end beingopen for the dischar of hot products of combustion, the combination ofnon-expanding nozzle means associated with each of said ports forstabilizing the direction of jet discharge into the liner, each nozzlehaving a rounded contracting entrance and being arranged with its axisnormal to the axis of the liner and extending radially outward from theinner surface of the liner, the nozzles adjacent the closed end of theliner having an axial length of the order of five-eighths the innerdiameter of the nozzle, the remaining nozzles be- 10 ing ofprogressively shorter axial length toward the discharge end of the linerwhereby the specing of the inlet ends of the nozzles from the outerhousing provides unimpeded access of the air to said inlets.

4. In a fluid fuel combustor of the type having an elongated liner ofcircular cross-section tapering from a minor diameter at one end to amajor diameter at the other end and-defining a combustion space within,said liner having a plurality of circumferentially spaced longitudinalrows of ports adapted to admit combustion air in discrete radial jets,and-an end dome member closing the small endof the liner, the larger endbeing open for the discharge of hot products of combustion, thecombination of non-expanding nozzle means associated with each of saidports for stabilizing the direction of jet discharge into the liner,each nozzle being arranged with it axis normal to the axis of the linerand extending radially outward from the inner surface of the liner, thenozzles adjacent the closed end of the liner having rounded contractingentrances and an axial length of the order of five-eighths the innerdiameter of the nozzle.

5. In a fluid fuel combustor of the type having a substantiallycylindrical liner with a plurality of circumferentially spacedlongitudinal rows of ports for admitting combustion air in radialdiscrete jets, the combination of non-expanding nozzle means associatedwith each port and extending radially outward from the inner surface ofthe liner for stabilizing the direction of jet discharge into the liner,the axes of said nozzles being normal to the axis of the liner, eachnozzle having a rounded contracting entrance and an axial length of theorder of five-eighths the inner diameter of the nozzle.

6. In a fluid fuel combustor of the type having a liner defining acombustion space and having a plurality of spaced openings adapted toadmit combustion air in strong discrete jets the direction of which isimportant to establishment of a desired flow path inside the liner, thecombination of separate non-expanding nozzle means associated with eachopening and extending from the inner surface of the liner radiallyoutward i'or stabilizing the direction of the jet discharged into theliner, each of the nozzles having a well rounded contracting entranceportion and a cylindrical discharge portion and an overall axial lengthof the order of five-eighths the inner diameter of the nozzle.

'7. In a fluid fuel combustor having an elongated liner of substantiallycircular cross-section defining a combustion space within, and an enddome member closing one end of the liner and having ports for theadmission of air to the combustion space, the combination of wallsdefining an outer casing enclosing the liner and end dome and spacedfrom each to define therewith an air supply chamber, said walls alsoforming an inlet opening for receiving air under pressure, thecombination of shroud means spaced from and enclosing said end dome andhaving ports adapted to supply air uniformly to the end dome ports atsubstantially the pressure ofthe air supplied to the inlet of saidcasing whereby the direction of the jets from the end dome ports issubstantially unaffected by unsymmetricity or changes in the directionof approach of the air entering through said inlet opening.

8. In a combustion device of the type having an elongated liner ofcircular cross-section tapering from a minor diameter at one end to amajor diameter at the other end and defining a combustion space within,said liner having a plurality of circumferentiaily spaced longitudinalrows of ports adapted to admit combustion air in discrete radial Jets,an end dome member closing the small end of the liner and having louversfor admitting jets of air, the larger end being open for the dischargeof hot products of combustion, the combination of non-expanding nozzlemeans associated with said ports for stabilizing the direction of jetdischarge into the liner, each nozzle having a well-rounded contractingentrance and a non-expanding discharge portion and extending radiallyoutward from the inner surface of the liner, the nozzles adjacent theclosed end of the liner having an overall axial length of the order offive-eighths the inner diameter of the nozzle, the remaining nozzlesbeing of progressively shorter axial length toward the discharge end ofthe liner, shroud means spaced from and enclosing said end dome andhaving ports adapted to supply air uniformly to the end dome louvers, anouter cylindricalcasing surrounding the liner and spaced therefrom todefine a combustion air supply chamber, the downstream end of the casingterminating in an edge portion substantially co-planar with thedischarge edge of the open end of the liner, an air inlet adapter membersecured to the upstream member defining a conduit for causing air toapproach the dome end of the liner in a direction substantially atninety degrees to the axis of the liner, means securing said shroud tosaid air adapter for supporting the inlet end of the liner assembly, andmeans slidably supporting the discharge end of the liner assembly fromthe outer casing, said means including an annular support member havingan outer circumferential edge portion adapted to be secured to thedownstream end of the outer casing, an inner supporting portion definingan inner cylindrical surface adapted to surround and slidably engage theouter surface of the discharge end of the liner, and an intermediateportion defining an annular convolution whereby diflerentiai thermalexpansion between said inner and outer "circumferential portions may"occur without distortion of the liner end portion.

. KENTON D. MCMAHAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNI'I'ED STATES PATENTS Number Name Date 1,696,668 Button Dec. 25, 19282,072,731 Crosby Mar. 2, 1937 2,398,654 Lubbock Apr. 16, 1946 2,475,911Nathan July 12, 1949

